Oligoryzomys nigripes

Oligoryzomys nigripes, also known as the black-footed colilargo or the black-footed pygmy rice rat, is a rodent in the genus Oligoryzomys of family Cricetidae. It is found from Pernambuco in northeastern Brazil through the Atlantic Forest and Cerrado into Paraguay, Uruguay, and Argentina, where it occurs in the provinces of Chaco, Misiones, and Buenos Aires. Two other species, Oligoryzomys delticola (also known as the delta pygmy rice rat or the large colilargo) and Oligoryzomys eliurus (also known as the Brazilian pygmy rice rat or the Brazilian colilargo) have been recognized as synonyms of O. nigripes since 2005; they cannot be distinguished on the basis of morphology, karyotype, or morphometrics. It is a large species with long ears, dark yellow to dark brown upperparts, sharply delimited from the whitish underparts, and often a pink girdle on the chest. The karyotype is 2n = 62, FNa = 78–82.